Current ocean science requires real or near real time subsurface data to support models of ocean processes. Parameters such as temperature and salinity, among many others, may be monitored by instruments mounted on oceanographic moorings. To enhance system survivability these moorings are frequently of subsurface design having no surface expression. Instruments may be mounted in fixed positions but an increasingly common method for obtaining such data involves moving, or profiling, instruments through the water column to obtain profiles of oceanographic conditions. Since the desired sites for these data are frequently far from shore, some form of communication link, typically via satellite, is required. The problem with known systems is the secure and stable intermittent maintenance of an antenna above an unstable sea surface at a fixed mooring site using a surface buoy while at the same time ensuring that the surface expression does not compromise the scientific data being collected, or interfere with the performance of the subsurface portion of a mooring or profiling system.
Simply placing an antenna on the top of an intermittently surfacing element is not a viable option when working in a moored configuration. The transmission of data from the subsurface portion of a mooring is problematical when the surface of the ocean is perturbed by waves. Because of wave forcing, it is difficult to avoid submergence of the data transmitting element resulting in interruption of transmission. With any significant wave height, the antenna has to become inordinately large because the transmitting element is subjected to inertial forces caused by interaction of the orbital motion of the water and the transmitting element's self and virtual mass. These forces are transient in nature and can give rise to snap loadings that may have deleterious effects on all components of the mooring's system.
As a specific example, U.S. Pat. No. 6,463,800 discloses a moored buoyant ocean profiler that includes a counterbalancing buoyant member for conserving energy as the instrument carrying buoyant member is raised and lowered. In this particular case, when the instrument carrying buoyant member is raised for transmission into the wave zone the balance of the profiler drive system, upon which the energy efficient system relies, can be upset.
The approach developed to overcome these obstacles, including the energy conserving system described above, was to provide a separate communication float connected to the instrument carrying submerged buoy by a flexible line.
U.S. Pat. No. 6,397,510 discloses a fishing bobber with strike-indicating radio transmitter for transmitting a radio signal to the fisherman when there is a strike on the line. Although one embodiment of this patent shows separate transmitter float for communication purposes, the arrangement as shown is not intended for, nor, would it be suitable for meeting the requirements of the present invention, such as when it subjected to wave action on the ocean.